Republican presidential hopeful Rick Santorum has released his four years of tax returns Wednesday.  His rate of tax returns for the years 2007-10, which is between 25.4 percent and 28.5 percent, is quite normal.  It is much higher than Mitt Romney's 15 percent of tax rate but lesser than Newt Gingrich's projected 33 percent.

However, Santorum's tax returns reveal some interesting figures that might bring him under the scrutiny of his opponents as well as the Republican conservatives. Santorum is selling himself in the Republican presidential race as the most conservative candidate who is rooted in Christian values and the church.

In fact, it is Santorum's ultra conservative philosophy and his religious way of life that is his USP for his claim to the Republican presidential nomination. But interestingly his tax returns tell a different story about his religious ways.

Christians are expected to give a certain part of their income to church and charity. According to the Old Testament, the rate of such offerings should be ten percent and the very practice is called tithing which means one tenth part of something. There are several mentions in the Bible on tithing by devotees.

The New Testament also supports charity but doesn't exactly prescribe a rate but instead says the contribution should be proportional to one's income, consistent, sacrificial and cheerful. However, the traditional perception on contributions to the church or charity is that it should be at least 10 percent of one's gross income.

But interestingly, though Santorum is staunch believer, his contributions to charity is nominal when compared to that of Romney or even President Obama.

In 2008, Santorum reported an Adjusted Gross Income (AGI) of $659,637, as per his tax returns. His deduction under the charity head is $13,383 for the year, which is just 2.2 percent of his AGI.  In 2008, he paid $21,990 to charity on his AGI of $945,100, at the rate of 2.33 percent.

For the year 2009, Santorum's returns show that he has paid $29,822 to charity while his AGI is more than $1 million (1,116,736). That translates in to 2.67 percent of AGI to charity.

In 2010, he paid $16,289 to charity on his AGI of $923,411, at the rate of just 1.76 percent. So roughly calculating, Santorum has just paid 2 percent of his $4 million income in the four years to church and charity, while he is expected to pay a minimum of 10 percent.

So when we consider Santorum's income, the percentage he is donating to charity is not a tithing (as it is less than 10 percent) as per the Old Testament or traditional guidelines, nor does it meet the New Testament guidelines, which say it should be proportional and sacrificial. At any case, a 2 percent on a near million income cannot be regarded as sacrificial- it isn't consistent either.

Santorum has always touted his humble beginning and staunch religious views. Though he says he has modest means, his tax returns show that he is almost a millionaire. Though not as wealthy as Romney or Gingrich, yet he is certainly well off as per the U.S. government income guidelines, which say any family which has income of around $5500 per head is not poor.

Therefore, Santorum would really find it difficult to justify his very low rate of charity donations. Especially, when his GOP opponent Romney pays more than 15 percent to charity, which in fact is more than what he pays in taxes. Even a Democrat President Obama reportedly pays around 5 percent to charity.

If his opponents decide to leverage on this information, then Santorum for sure have sleepless nights ahead.